Waltek s



W. S. LANDIS.

CATALYZER FOR OXI DIZING AMMONIA. APPLICATION FILED 1mm, 1916.

1,193,800 Patented Aug. 8, 1916.

zgwuemho z WaLCer' S. Lem/dis, 4y

Gum/way UNITED OFFICE.

WALTER s. mums, or ruw roan, 1mm, ammo rmx s. WASI-IBUBN, or

. I NASHVILLE, TENNESSEE.

cA'rnLYzEn FOR oxrnrzmo AMMONIA.

' Specification of Letters Patent.

Original application flied February 20,1915, Serial No. 9,596. Dividedand this application filed January 27, 1916. Serial No. 74,673.

oxidizing ammonia and has for its object to produce nitrose gases in amanner more efficient and less costly than has been heretofore proposed.

With these andother objects in view the invention consists in the novelconstruction constituting my ap aratus, all as will be more fullyhereinaer disclosed and particularly pointed out in the claims.

In my copending application, Serial No. I

9596 filed February 20, 1915, and entitled u Processof and apparatus foroxidizing am- I monia, of which this application is a division, Idisclose and claim a method of oxidizingammonia for which the apparatusmade the subject of this application is suitable. Also in my copendingapplication Serial No. 9595, filed February 20,1915 and entitled Methodof oxidizing ammonia I disclose certain reactions that are involved inthe oxidation of ammonia to nitrose gases,

and how'the precooling of the gas mixture before striking the catalyzergives rise to a much higher efliciency than is found in the oldermethods which do not employ-this cooling action. But in the use of acooler there is naturally brought forward prorninently the necessity 10fproviding special means for supplying the required amount of outsideheat, to the reacting mixture in order that the flame may burncontinuously.

I have found that when one uses an ammonia air mixture in the proportionof one volume of ammonia to 15 volumes of air the resulting flametemperature is'only about 460 C. and inasmuch as this combustiontakes'place best at temperaturesof slightly above 700 C. I .find withsuch proportions 2670 cals. per cubic meter of ammonia Patented Aug. 8,191 16. 7

burned. Even in case one oper'ateswith a mixture of one volume ofammonia to ten volumes of air the resulting flame temperature is only640 C. and there is a deficiency of 470 cals. per cubic meter ofammonia" burned. On. the other hand, similar calculations show that if amixture of one volume of ammonia to 7% volumes of air could be used theresulting flame temperature, allow ing for slight losses, would be justabout right for the proper working of the catalyzer. But again, when amixture of am monia and air containing less air than .one volume ofammonia to ten volumes of air is used it does not operate well from achemicalvariable amount of heat, the quantity vdepending upon the ratioof ammonia to air which one desired to use. Of course, if one uses anenriched air, such as the waste gases from a liquid air plant, producingnitrogen,

or if one employs purposely enriched gases made by introducing'oxygeninto air in any well known manner, this deficiencyof heat 1 willdisappear with an increase of the oxygen content of the air used. It ishowever, necessary to meet a varying 'heat requirement in the reaction,even when operating with various kinds and proportions of enriched air.j

It is under all circumstances necessary to supply heat inorder to startthe reaction going, and this can best be done by preheating thecatalyzer until the flame ignites" and burns steadily. I, therefore, seethat in a commercial operation of an ammonia oxi dation plant it isnecessary to provide means, not only of heating the catalyzer, but ofcontrolling .the amount of heat one supplies to this apparatus.

I am well awarethat the most advantageous system of supplying heat thatmust be accurately controlled, is through transformposition of asuitable resistance.

7 trolling means 5.

ing electrical energy into heat by the inter- And the ease with whichthis electrically generated heat can be controlled to an exactness whichis so essential to this process makes it an added feature'of theprocess.

I am also aware that many years ago laboratory experiments were carriedout in which platinum spirals were heated in a current of an ammonia-airmixture, forming nitric acid. These experiments, however, were only ofscientific interest because the yields were extremely low and a verylarge percentage of nitric acid which might have been formed wassubsequently decomposed by remaining in contact with the electricallyheated spirals. The objections to the above processes have been overcomeby my process now to be disclosed. That is to say, I have discovered aprinciple by which high efficiencies of oxidation are attained on acommercial scale, adapted to produce hundreds of pounds of nitric aciddaily. In the first place, I use a new form of catalyzer, coupled withthe use of electrical energy for supplying the necessary heat tomaintain the necessary reacting temperature in the apparatus.

The previous forms of catalyzers used so far as Iam aware have consistedof platinum tubes, various complex combinations of sheets and tubes,interlacing of platinum sheet, platinized mica, and even platinizedasbestos as well as platinum sponge. None of these, however, lendthemselves readily to electrical heating because their construction doesnot afford a uniform resistance throughout the catalyzer, and therefore,there will be some local overheating should an electrical current bepassed through them. It is very important in this processthat thecatalyzer be absolutely uniformly heated, as exact temperature controlis an important part of the oxidation process. I therefore,

use for my catalyzer a gauze or fabric woven from uniformly drawnplatinum wire, and supported on a suitable frame, all as will be clearfrom the accompanying drawings forming a part of this specification inwhich Figure 1 is a diagrammatic plan view of a catalyzer. apparatusmade in accordance With my invention; and Fig. 2 illustrates anoxidation chamber containing a cooler associated with such'a catalyzingdevice.

In the said drawings 1 represents any suitable frame preferably ofinsulating material upon which is mounted the platinum mesh or wirecloth 2; The said cloth or meslr2 is joined in the circuit 3 with asuitable generator or other source of current 4 and with the rheostat orother current con- By employing one or more catalyzers such asillustrated in the oxidation chamber 12,

provided with a cooler 13, inlet 14, and outlet 15 in the mannerdisclosed in my said application, Serial No. 9595 above, I can heat thecatalyzer material uniformly with an electric current, and by means of asuitable rheostat can maintain the temperature at any point desired.

I have found thatthe platinum gauze with wires of say .005 of an inch indiameter or less, and with meshes of say 60 to the inch serves verywell, and that the diameter of the wire and number of meshes have littleinfluence provided they are of dimensions less than those above stated.By inserting such a catalyzer in my apparatus I can heat it electricallyto the desired temperature, and pass a current of an ammonia-air mixturethrough it attaining practically 100% efficiency in oxidation.

By means of the electrical control, consisting of either a resistance ora variable voltage transformer I can vary the heat generated in thisform of catalyzer to correspond to the varying proportions of ammonia toair in the mixture, whether using air alone, or oxygen enriched air. Orin case I have suflicient oxygen in my enriched air, I can simply usethis electrical energy for starting the reaction, after which it willtake care of itself.

In case the amm0nia-air mixture is not enriched by oxygen, it is founddesirable to uniformly heat the catalyzer material above 500 C. andusually up to about 700 C. or higher, depending on the proportions ofair and ammonia actually employed. It is also desirable to cool themixture as much as possible before subjecting it to the action of thecatalyzer, and to this end I may cool the mixture to any desired degreeby passing it through suitable refrigerating coils before leading it tothe oxidizing chamber, thereby facilitating the further cooling actionof the apparatus 13in said chamber. The best form of catalyzer I havefound for this purpose, is one made of iridium free platinum. In otherwords, I find if even a very small quantity of iridium is present in theplat inum, it greatly decreases the efliciency of the catalyzer.

It is evident that those skilled in the art may vary the details of myapparatus without departing from the spirit of the invention, andtherefore I do not wish to be limited to the above disclosure except asmay be required by the claims.

What I claim is 1. The herein described new catalyzer element comprisinga wire gauze of iridium free platinum.

2. The herein described new catalyzer element comprising a wire gauzewoven from a uniformly drawn wire of iridium free platinum.

.3. The herein described new catalyzer element comprising a wire gauzefabric com- In testimony whereof I afiix my signature, posed 'ofuniformly drawn wire of iridium in presence of two Witnesses.

free platinum joined in an electric circuit, WALTER S. LANDIS. combinedwith means for controlling the Witnesses: 5 energy passing through saidcircuit, sub- G. M. SOHURMAN,

stantially as described. S. W. MAYS.

